New Technique Harvests Stem Cells at Earlier Stage

Research shows future production of new lines may be done without destroying embryo

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WEDNESDAY, July 9, 2008 (HealthDay News) -- Scientists say they have finally succeeded in developing human embryonic stem cells earlier in the development stage of a blastomere, or a 4-cell stage embryo, so the whole embryo is not destroyed.

The development, expected to be presented Wednesday at the European Society of Human Reproduction & Embryology annual conference in Barcelona, may make stem cell research easier to conduct by not raising as many ethical concerns, the researchers added.

"Previously, scientists have been able to derive hESC [human embryonic stem cell] lines at the 8-cell stage," Hilde Van de Velde of the Vrije Universiteit Brussel, Brussels, Belgium, said in a news release issued by the society, "but success rates were variable, and it was necessary to culture them by mixing with established hESC lines. We have been able to derive hESCs at an earlier stage of embryonic development, and without the need for co-culture with established hESC lines. Now we have derived a second hESC from one cell of a 4-cell stage embryo. Given the complex nature of earlier attempts, we were pleased that we could develop a technique that seemed simple and was also reproducible."

Blastomeres form in the early stages of embryonic development when important changes occur: inner cells become the fetus, and outer cells change into trophoblast, the outermost layer of the embryo that hooks into the uterus and becomes a feeding tube for the developing egg.

Working with mature eggs donated by couples undergoing in vitro fertilization, researchers split three 4-cell stage embryos into a dozen single blastomeres. They then allowed them to grow in vitro and cultured them using conventional methods for hESC derivation. From these 12, one resulted in a stable hESC line, including one that scientists determined was pluripotent, or derived from the inner cells at the blastocyst stage, just as most other established hESC lines are.

"Now we will try to derive four hESC lines from the same embryo in order to compare the potency capacity of all four cells," Van de Velde said.

The work could have major ramifications for pre-implantation genetic diagnosis (PGD), by enabling the biopsy of one cell from a 4-cell stage embryo. This would let the remaining three cells grow into a blastocyst (five-day embryo) that could be implanted into the uterus and develop into a healthy baby.

"Currently, PGD is performed at the 8-cell stage, when one or two cells are removed; others have derived stable hESC lines at this stage but with low efficiency. If hESC derivation at the 4-cell stage turns out to be more efficient then at the 8-cell stage, we might consider changing our PGD policy," Van de Velde said.

The public mostly favors stem cell research, according to another researcher scheduled to speak at the conference.

According to the online survey of almost 600 people, more than 78 percent disagreed or strongly disagreed with the statement "I believe that it is morally wrong to use embryonic stem cells for research." A similar majority also disagreed with the statement "I believe that it is morally wrong to use embryonic stem cells for medical treatment."

"We found no difference between male and female attitudes towards using hESCs for research, but when it came to medical treatment, men showed significantly more support than women," survey researcher Jaclyn Friedman, a clinical embryologist at Reproductive Biology Associates in Atlanta, said in a news release from the society. "We found no significant differences when we looked at particular age groups, but a higher level education of respondents correlated with greater support for the use of hESCs, both in research and medical treatment. There were no important differences among regions of the world ..."

"Our study shows that public, patient, and scientific opinion is very much in favor of both stem cell research and the therapeutic use of stem cells in medical treatment. This is different from the perceived equal distribution for and against hESC use reported in the news media," she said.